Investigation of boiling heat transfer in an electrically heated tube bundle

The paper presents the results of experimental research on water, methanol and R141b refrigerant boiling in a horizontal bundle of smooth tubes supposed to represent part of a flooded evaporator. Experiments were carried out for a bundle of 19 tubes in triangular layout for two spacing-to-diameter ratio values -1.7 and 2.0 - in atmospheric and subatmospheric pressure conditions. Heat transfer coefficient values - both local, tube-specific, and general, for the entire bundle - were determined. The boiling process at the bundle was visualized with a CCD camera and laser sheet technique. A correlation equation allowing the calculation of the average heat transfer coefficient for boiling in smooth tube bundles has been proposed.